Jumper cables are used to connect the relatively weak battery, incapable of starting the engine in the vehicle in which it is located, to a relatively strong battery in another automotive vehicle. Essentially the jumper cables are nothing more than two wires capable of carrying the current involved, with clips at each end of each of the wires to releasably engage the terminals on the batteries involved.
In the use of such conventional cables there is a very serious danger to the persons who are making this temporary connection between the two batteries through the use of the cables. This danger is occasioned by the fact that the storage batteries conventionally employed in automotive vehicles give off hydrogen. That hydrogen in the presence of the ambient air can produce explosive atmospheres. Such explosive atmosphere may be present within the battery case as well as immediately adjacent the battery. It is not uncommon for the hydrogen outside of the battery to ignite and in turn ignite the hydrogen within the battery, causing the battery to explode. When the battery explodes the acid within the battery is thrown about and can cause serious burns to personnel involved. People have had eye damage result from being splashed with acid from batteries so exploding. What happens is that in making the temporary connections through the use of the jumper cables, a spark occurs between the last of the four clips being connected and the battery terminal to which that last connection is made. The battery terminal is, of course, on the battery and thus in close proximity to the hydrogen that may be present around that battery. While the manufacturers and vendors of battery cables usually supply instructions warning users to make the last connections at a point remote from the battery, e.g., perhaps at a location on a frame of the vehicle (the frame being connected in the vehicle to a "grounded" battery terminal), such instructions are often disregarded with serious consequences.
The principal object of the present invention is to provide a battery cable assembly by which it is virtually impossible to create a spark at a location at which the battery hydrogen will be present. Thus even though the user of the cable is careless or inattentive in making the battery connections with the cable, that person's actions will not result in a battery explosion. This is achieved by using a relay intermediate the ends of the battery cable. Since the relay contacts are normally open there is no possibility of the battery cables carrying current while the cable is being connected to, or disconnected from, the battery. After such connections to the batteries have been made, a remote push button switch is actuated to energize the relay solenoid which acts to close the relay contacts and create electrical connections between the ends of the battery cables. While a spark may occur at the relay contact this is at a location remote from the batteries and inside a relay case and thus at a location where it is virtually impossible for any of the battery hydrogen to be present. The fact that the relay is approximately centered between the ends of the battery cables necessarily dictates that it be remote from the two batteries involved, since the size and configuration of the vehicles involved necessarily dictates a substantial distance between the ends of the jumper cable. This fact in association with the overall length of the jumper cable will virtually prevent a person from locating the relay closely adjacent one of the batteries.
A further advantage in embodiments of the invention reside in the presence of the push button switch for actuating the relay at the end of a cable which connects to the relay. This permits, for example, a person to be in the driver's seat of the disabled vehicle and operate the engine controls of that vehicle at the same time that the switch is being actuated to connect the two batteries.